From the names you listed the Pittsburgh Pirates signed place mat can be dated to about 1968-1970. The value will be dictated by the Roberto Clemente signature. Assuming that the signatures are hand signed, not facsimile, and without seeing how well the place mat displays the signatures I will estimate the value based on a Roberto Clemente cut signature, at about $500.-$1,000.
Value is based on past auctions and sales, and will vary based on the condition of the place mat, grade of the signature, placement & display. If there is any interference from the background printing behind the signature, or other signatures the value will be lowered. Signatures that are not properly authenticated could sell at half the market value or less.
If you post a picture of the place mat I might be able to help you with a more accurate estimate. -Steven KeyMan
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